Hydropneumatic pressure reservoirs are disclosed, for example, in DE 25 34 361 B2. Because of the very narrow tolerances, such as must be observed in the case of wall components used in conjunction with each other in the connecting area of the housing shells and of the surfaces coming in contact with the edge area of the diaphragm, installation of the diaphragm and assembly of the housing shells tend to be a relatively difficult process. Because of the precise fit required, the smallest errors in alignment or inclination relative to the longitudinal axis during assembly of the components result in disruption of the assembly process or even in damage from misalignment or tilting.
EP 1 031 729 A2 discloses a generic hydropneumatic pressure reservoir, with a retaining device for the partition or separating diaphragm comprising a self-contained fastening ring which fastens two housing shells held together under tension. The fastening ring, as the retaining device, forces a diaphragm bead on the end side over a flange-like metal ring into the associated seat in the lower housing shell of the reservoir. In the area of the respective bead seat for the partition or separating diaphragm, the housing shells are cylindrical in shape on their guide surfaces facing each other, and consequently, are in contact with each other. The fastening ring and the lower housing shell extend over a predetermined area below the fastening bead with retaining surfaces extending parallel to and equidistant from each other to delimit a gap, and thus, maintain the partition over a predetermined distance. If the housing shells come in contact with each other during assembly of the disclosed reservoir, contact mismatch may occur even with precisely worked guide and retaining surfaces. Such contact mismatch impairs the clamping of the diaphragm and its later fastening in the reservoir, and may also greatly complicate assembly. The sealing ring mounted between the cylindrical guide surfaces of the two housing halves, which accordingly is positioned outside the diaphragm fastening point, is subjected to no additional clamping force increasing the sealing force. Thus, tightness problems may arise especially in the event of inaccurate clamping within the framework of the assembly as described.